It's an action game more in the style of DMC. The other heroes with you serve the main purpose of transforming into weapons (giant fists, gun, swords, etc.). They can be used in other ways, too, such as having them jump on to enemies to momentarily stun them and do extra damage. They've said you can use them in a variety of other ways, but we won't know for sure until the game is out.

Here's the blog for Platinum, where they've been detailing the mechanics more in depth:

Thought this was a rather clear post about the genre. I know people are getting somewhat confused based on the nature of having 100 heroes at a time, thinking it's like Pikmin, but it's an action game. The best way to think of the other heroes in 101 is that they are basically your weapon of the game. Instead of a regular fist or sword or gun, they morph into said weapon. They will be able to utilized in other ways, but that's the core of it.

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"When you see a John Woo film, it's comforting to know how shallow the world really is. The full force of the manly coolness factor with a peice of nose hair sticking out from the tiny crack between manly and cool, exposes the thinness of the male hormone factor. It takes an idiot to do cool things. That's why it's cool."

Quote:

I was a North American Fall Webworm in my past life. Those were the good old days.